High-frequency chip packages
A packaged semiconductor chip includes features such as a chip carrier having a large thermal conductor which can be solder-bonded to a circuit board so as to provide enhanced thermal conductivity to the circuit board and electromagnetic shielding and a conductive enclosure which partially or completely surrounds the packaged chip to provide additional heat dissipation and shielding. The packaged unit may include both an active semiconductor chip and a passive element, desirably in the form of a chip, which includes resistors and capacitors. Inductors may be provided in whole or in part on the chip carrier. A module includes two circuits and an enclosure with a medial wall between the circuits to provide electromagnetic shielding between the circuits.
Latest Tessera, Inc Patents:
- Method and structure for forming dielectric isolated FinFET with improved source/drain epitaxy
- Homogeneous densification of fill layers for controlled reveal of vertical fins
- Nanosheet field effect transistors with partial inside spacers
- Selective gas etching for self-aligned pattern transfer
- Hybrid-channel nano-sheet FETS
This application is the National Stage of International Application No. PCT/US02/27509, filed Aug. 28, 2002, designating the United States. Said international application claims the benefit of U.S. Provisional Patent Application No. 60/315,408 filed Aug. 28, 2001. Said international application is also a continuation-in-part of U.S. patent application Ser. No. 10/219,160, filed Aug. 1, 2002, which application also claims the benefit of said U.S. Provisional Patent Application No. 60/315,408. The disclosure of all of the aforesaid applications are hereby incorporated by reference herein.
BACKGROUND OF THE INVENTIONThe present application relates to the art of packaging microelectronic elements such as semiconductor chips.
Semiconductor chips or dies commonly are provided in packages which facilitate handling of the chip during manufacture and mounting of the chip on an external substrate such as a circuit board or other circuit panel. For example, certain packaged semiconductor chips sold under the registered trademark μBGA® by Tessera, Inc., assignee of the present application, incorporate a dielectric element having terminals. The terminals are connected to contacts on the die itself. In particularly preferred arrangements, the connections between the terminals and the die are formed by flexible leads and the dielectric element, its mounting to the die or both are arranged so that the terminals remain moveable with respect to the chip. For example, where the dielectric element overlies a surface of the chip, a layer of a compliant material may be provided between the dielectric element and the chip. The packaged chip can be mounted to a circuit board or other underlying circuit panel by soldering or otherwise bonding the terminals on the dielectric element to contact pads on the circuit board. Because the terminals on the dielectric element can move relative to the chip, the assembly can compensate for differential thermal expansion and contraction of the chip and the circuit board during thermal cycling in service, in storage and during manufacturing processes.
Assemblies of this type are described, for example, in U.S. Pat. Nos. 5,148,265; 5,148,266; and 5,679,977. In certain embodiments, the leads can be formed partially or wholly as elongated metallic strips extending from the terminals along the dielectric element. These strips can be connected to the contacts on the chip by wire bonds, so that the wire bonds and strips cooperatively constitute composite leads. In other embodiments, the strips themselves can be connected directly to the terminals. Certain methods of forming strip-like leads and connecting numerous strip-like leads to numerous contacts on a die are described in U.S. Pat. Nos. 6,054,756; 5,915,752; 5,787,581; 5,536,909; 5,390,844; 5,491,302; 5,821,609; and 6,081,035, the disclosures of which are incorporated by reference herein.
The aforementioned structures, in their preferred embodiments, provide packaged chips with numerous advantageous including the aforementioned ability to compensate for differential thermal expansion and hence high reliability; compatibility with surface-mounting techniques for assembling components to a circuit board and the ability to accommodate numerous connections to the chip in a compact assembly. Some of these packages occupy an area of the circuit board just slightly larger than the area of the chip itself. Certain preferred packages of this type provide short, strip-like leads which minimize self-inductance in the leads and hence provide good high-frequency signal propagation. Moreover, certain packages according to this design can provide good heat dissipation from the chip. These packages have been widely adopted for semiconductor chips in numerous applications.
However, despite these advancements in the art, still further improvement and optimization would be desirable. Chips used for generating or processing radio frequency (“RF”) signals, commonly referred to as “RF chips”, are used in numerous devices including cellular telephones and wireless data communication devices. RF chips typically generate substantial amounts of heat. Although RF chips typically have only a moderate number of input/output connections, and hence require only a moderate number of connections to the circuit board, these connections should be made with low-inductance leads having controlled, predictable impendence at the frequencies handled by the chip. The packages for RF chips should be compact and economical. Moreover, it would be desirable to provide packages which are particularly well suited to RF chips using the same production equipment and techniques used with other package designs as, for example, the μBGA® chips.
SUMMARY OF THE INVENTIONOne aspect of the present invention provides a semiconductor chip assembly. A semiconductor chip assembly according to this aspect of the invention desirably includes a packaged semiconductor chip incorporating a semiconductor die having a front surface, a rear surface and contacts exposed at the front surface. The packaged semiconductor chip also includes a chip carrier having inner and outer surfaces. The inner surface of the chip carrier faces toward the front surface of the die. The chip carrier also has a plurality of terminals and a thermally conductor, preferably formed from a metallic material, exposed at the outer surface of the chip carrier. The thermal conductor has a relatively large area, substantially larger than the area of each individual terminal. The thermal conductor may have an area of at least 10 times, and desirably at least 20 times, the area of a single terminal. The thermal conductor is at least partially aligned with the die. The terminals on the chip carrier optionally may be movable with respect to the die. The thermal conductor optionally may be movable with respect to the die. An encapsulant layer may be provided between the die and the chip carrier, and between the die and the thermal conductor.
The circuit panel has contact pads and has a thermal conductor mounting. The pads and thermal conductor mounting typically are metallic. The packaged chip is disposed on the circuit panel so that the outer surface of the chip carrier faces toward the circuit panel. The terminals of the chip carrier are bonded to the contact pads of the circuit panel. Most desirably, the thermal conductor of the chip carrier is also bonded to the thermal conductor mounting of the circuit panel, and this bond preferably is a metallurgical bond. As used in the disclosure, the term “metallurgical bond” refers to a connection between elements formed substantially or entirely from one or more metals or alloys. The thermal conductor and the bond between the thermal conductor and the thermal conductor mounting on the circuit panel provide a low thermal resistance cooling path between the packaged chip and the circuit panel. Moreover, the thermal conductor can attenuate undesired RF emissions from the chip and/or RF signals impinging on the chip from other portions of the circuit, and can also be referred to as a “shield.” Most desirably, the thermal conductor mounting of the circuit panel is connected to a ground or power voltage source and the thermal conductor is electrically connected to one or more ground or power contacts on the die by thermal conductor leads similar to those used to connect the other contacts with the terminals. Thus, the thermal conductor can act as a very large ground or power terminal. Because the thermal conductor has a substantial horizontal extent, the thermal conductor can also act as a ground or power distribution bus; in this case, the thermal conductor is electrically connected to numerous ground contacts or numerous power contacts at widely spaced locations on the die. In a variant of this approach, the thermal conductor may serve as a clock terminal and/or clock distribution bus, in which case the thermal conductor mount on the circuit panel is connected to a clock signal bus so that the clock signal is routed between the clock signal bus and the clock contacts of the chip.
In certain embodiments, the packaged chip may include a metallic heat spreader or “can” having a main or top wall structure overlying the rear surface of the chip so that a portion of the heat spreader faces upwardly, away from the circuit panel when the packaged chip is assembled to the circuit panel. The heat spreader desirably has a side wall projecting from the main portion of the heat spreader towards the front surface of the die. This wall desirably terminates in a horizontal surface or flange. In the assembly, the horizontal surface or flange of the heat spreader desirably is metallurgically bonded to a spreader mounting on the circuit panel. The spreader facilitates heat transfer from the packaged chip into the surroundings, away from the circuit panel. Where the spreader is bonded to the circuit panel, the spreader can also facilitate transfer of heat from the packaged chip into the circuit panel. The spreader can also serve as an RF shield, as a ground connection to the rear surface of the chip, or both. In an alternative arrangement, the side wall structure is bonded to a metallic feature on the chip carrier, which in turn is bonded to a mating feature of the circuit panel.
Yet another aspect of the invention provides packaged chips having features as discussed above in connection with the assembly.
A still further aspect of the invention provides connection components suitable for use in fabricating the packaged chips. Connection components according to this aspect of the invention most preferably include a dielectric layer having an inner surface and an outer surface, a metallic thermal conductor occupying at least a part of the dielectric layer, and terminals on the dielectric layer. The thermal conductor has an area substantially larger than the area of each individual terminal. The terminals and the thermal conductor are exposed at the outer surface of the dielectric layer. For example, the terminals and the thermal conductor may overlie the outer surface. Alternatively, the terminals and the thermal conductor may be disposed on the inner surface and openings in the dielectric layer may be provided in alignment with the terminals and the thermal conductor. The connection component desirably includes terminal leads electrically and physically connected to the terminals and most preferably includes one or more thermal conductor leads electrically and physically connected to the thermal conductor. The terminals, leads and thermal conductor are arranged so that when the leads are connected to the contacts on the die the thermal conductor overlies the front surface of the die. For example, the thermal conductor may be disposed in a central region of the dielectric layer, and at least some of the terminals may be disposed in a peripheral region of the dielectric layer surrounding the central region.
Most desirably, the terminals, lead and thermal conductor are all formed in a single metallization layer as, for example, by etching a single layer of metal. In one preferred arrangement, the leads extend across gaps in the dielectric layer so that the leads can be engaged with contacts on the chip during formation of a chip package by advancing a bonding tool into the gap so as to force the leads into engagement with the contacts on the chip. Most desirably, each lead includes a connection section which will be engaged with a contact on the chip and a frangible section weaker than the connection section. The frangible sections of the terminal leads may be disposed between the connection sections of these leads and the thermal conductor. Thus, prior to assembly with the chip, the terminals and terminal leads are electrically connected in common by the thermal conductor. However, when the frangible sections of the terminal leads are broken, the terminal leads are electrically disconnected from the thermal conductor. This allows use of the thermal conductor as a commoning bus during fabrication of the leads as, for example, in electroplating or etching operations.
A further aspect of the invention provides a packaged semiconductor chip. The packaged chip according to this aspect of the invention desirably includes a first semiconductor chip having an upwardly-facing front face, a downwardly-facing rear face, edges bounding said faces and contacts exposed at said front surface, said first semiconductor chip including active components. A connecting element including passive components such as resistors, capacitors and inductors is electrically connected to at least some of the contacts of the first chip. The connecting element overlies the front face of the first chip and projects outwardly beyond the edges of the first chip. A chip carrier is disposed below the rear surface of the first chip. The chip carrier has a bottom surface facing downwardly away from the first chip and has a plurality of terminals exposed at the bottom surface, at least some of such terminals being electrically connected to at least some of the contacts of the first chip through said connecting element. Most preferably, the connecting element is a second chip incorporating the passive elements, also referred to as a “passive chip.” The chip carrier may include a thermal conductor as discussed above, and may also include a spreader or enclosure having a top wall overlying the rear surface of the connecting element or passive chip. As discussed above, these features provide further enhanced thermal dissipation and electromagnetic shielding.
In a packaged chip according to a further aspect of the invention, the position and orientation of the first chip and the connecting element or passive chip are reversed, so that the first chip lies above the passive chip. In this arrangement, the front surface of the first or active chip faces downwardly and confronts the upwardly-facing surface of the second or passive chip. The rear surface of the passive chip faces downwardly, toward the chip carrier. Chip assemblies according to this aspect of the present invention may also include thermal conductors and spreaders as discussed above.
Yet another aspect of the present invention provides packaged modules including two separate microelectronic circuits a pair of separate radio frequency amplification circuits. A packaged module according to this aspect of the invention includes a carrier having top and bottom surfaces and having terminals exposed at the bottom surface. A first microelectronic unit or assemblage including one or more chips is mounted to the carrier and overlies a first region of the top surface. A second microelectronic unit or assemblage is also mounted to the carrier and overlies a second region of the chip carrier. The module according to this aspect of the invention most preferably includes a metallic enclosure having top wall structure extending above the microelectronic units or assemblages and side wall structure extending downwardly from the top wall structure to the vicinity of the carrier. The enclosure also desirably has a medial wall extending to the vicinity of said carrier between the first and second regions. The enclosure, and particularly the medial wall structure, electromagnetically shields the first and second microelectronic units or assemblages from one another. Moreover, the enclosure desirably is in thermal communication with the chip or chips included in the microelectronic units or assemblages. The preferred modules according to this aspect of the invention can be used, for example, to provide a surface-mountable RF amplification unit which incorporates a pair of separate radio frequency amplification circuits.
A further aspect of the invention provides a packaged surface acoustic wave or “SAW” device. The packaged device according to this aspect of the invention includes a SAW chip having an acoustically active region on its front surface. The SAW chip desirably is mounted front-face-down on a chip carrier having an inner surface and an outer surface so that the active region of the SAW chip front surface is aligned with a hole in the chip carrier. The front surface is sealingly connected to the chip carrier around the periphery of the hole, so that the active region of the SAW chip is maintained free of encapsulants and contaminants. Preferred structures according to this aspect of the invention can provide a thin, surface-mountable packaged SAW device at low cost.
Yet another aspect of the invention provides A packaged semiconductor chip assembly including a first semiconductor chip incorporating one or more active components together with a passive chip incorporating one or more passive components selected from the group consisting of resistors and capacitors. The packaged chip according to this aspect of the invention also includes a chip carrier having terminals thereon. The chips are secured to the chip carrier, and at least some of the terminals are connected to at least one of said chips. The packaged chip according to this aspect of the invention desirably includes at least one inductor defined at least in part by features on the chip carrier, the at least one inductor being connected to at least one of the chips. As further explained below, the use of a passive chip to provide at least some of the resistors and capacitors affords significant savings in space and cost as compared to the use of discrete passive components, whereas formation of the inductor at least in part on the chip carrier allows the use of thick, low-resistance windings in the inductor to provide inductors with a high quality factor or “Q.”
Still further aspects of the invention provide particular structures for inductors usable in the foregoing aspects of the invention and in other applications.
Additional aspects of the invention provide methods of mounting chips to circuit panels. Methods according to this aspect of the invention desirably use packaged chips or modules and circuit panels as discussed above. In a method according to this aspect of the invention, the terminals are bonded to the contact pads and the thermal conductor is bonded to the thermal conductor mounting in a single operation. Most preferably, the terminals and thermal conductor are soldered or otherwise metallurgically bonded to the contact pads and to the thermal conductor mounting. Preferably, the contact pads and the thermal conductor carry layers of solder before the packaged chip is assembled to the circuit panel. Alternatively, the solder may be provided on the contact pads and on the thermal conductor mounting of the circuit panel. In either case, the solder connections can be relatively thin layers of solder as, for example, 25-50 microns thick. Stated another way, the connection between the packaged chip and the circuit panel may be a “land grid array” rather than a ball grid array. The ability to use thin solder connections further enhances the electrical performance of the completed assembly, and minimizes the height of the assembly. Moreover, there is typically no need for a layer of dielectric material or “underfill” surrounding the solder connections between the connection component and the circuit panel. This simplifies the connection procedure. Where a heat spreader is to be bonded to a spreader mounting on the circuit board, the spreader desirably is provided in place on the chip package before the chip package is assembled to the circuit panel, and the spreader is bonded to the circuit panel in the same bonding operation used to bond the terminals and thermal conductor.
The features of the foregoing aspects of the invention can be combined with one another or used separately. Still other objects, features and advantages of the present invention will be more readily apparent from the detailed description of the preferred embodiments set forth below, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A few of the leads are thermal conductor leads 30. The thermal conductor leads are similar to the terminal leads except that the connection sections of the thermal conductor leads are connected directly to thermal conductor 20, without an intervening frangible section. The end of the connection section of each thermal conductor lead 30 remote from thermal conductor 20 is connected to a “dummy” terminal 22a by a frangible section 32. Thus, the frangible sections of the thermal conductor leads are disposed adjacent the outer edges of the bond windows 24, remote from thermal conductor 20.
The terminals, leads and thermal conductor form an electrically continuous structure. Thus, the leads can be plated or otherwise subjected to processes requiring electrical current without the need for any additional electrical commoning element. Preferably, the thermal conductor, leads and terminals are formed from a single layer of copper or copper alloy about 10-30 microns thick, more preferably about 15-20 microns thick, on the dielectric layer. A photoresist can be applied and patterned using conventional techniques so that regions of the copper or copper alloy layer can be selectively removed so as to leave the terminals, thermal conductor and leads in place. In other processes, the thermal conductor, leads and terminals can be formed by selective deposition of one or more metals, such as by patterning a photoresist and plating in areas which are not covered by the photoresist. The bond windows can be formed by etching the dielectric or by exposing the dielectric to radiation such as laser radiation. The fabrication procedure for the chip carrier can be essentially as shown and described in the patents incorporated by reference. Also, although the frangible sections 28 and 32 are illustrated in
In fabrication of the package semiconductor chip, a die 14 is juxtaposed with the chip carrier so that the front surface 35 of the die faces toward the chip carrier and so that contacts 34 on the die are substantially aligned with the bond windows and with the connection sections of the terminal leads. Desirably, the arrangement of the leads is selected so that ground contacts on the die are aligned with the thermal conductor leads. In one manufacturing process, the dielectric is supported temporarily above the front or contact bearing surface of the die by a porous layer formed from a plurality of compliant elements or “nubbins” 36 (
Following connection of the leads, the assembly is encapsulated by injecting a flowable, typically liquid encapsulant 40 between the die and the dielectric layer of the connection component. The encapsulant desirably also covers the edges 46 of the die, but does not cover the rear surface of the die. Techniques for applying an encapsulant are disclosed, for example, in U.S. Pat. Nos. 5,766,987; 6,049,972; and 6,046,076, the disclosures of which are also incorporated by reference herein. Typically, several connection components are provided as sections of a single dielectric layer tape, which incorporates several sets of terminals and several thermal conductors as aforesaid. Several chips are assembled to the various sets of terminals, and encapsulated, whereupon the tape is severed to provide individual packaged chips.
Other manufacturing processes can be employed. For example, the die can be attached to the connection component by a preformed pad of an adhesive material or “die attach” disposed between the front face 35 of the die and the connection component. Such a pad can be provided as a part of the connection component, or applied during the assembly operation. In another technique, die attach material is provided between the front face of the die and the connection component by dispensing a mass of uncured, flowable die attach onto the connection component or onto the die before assembling the die to the connection component.
After encapsulation, the packaged semiconductor chip has the configuration shown in
In this embodiment, the terminals are disposed outside of the lateral edges 46 of the die. Stated another way, the terminals “fan out” from the die. Because the encapsulant is not directly loaded in shear between a terminal overlying the surface of the die and the die itself, substantial movability of the terminals can be achieved even with an encapsulant having a substantial shear modulus and a substantial modulus of elasticity. Typical encapsulants such as silicone gels tend to have coefficients of thermal expansion (“CTE”) substantially greater than that of the die and substantially greater than that of a circuit board to which the packaged chip will be mounted. In a fan-out structure, the fatigue stresses imposed on the leads during thermal cycling arise to some extent from the expansion of the encapsulant itself. Therefore, it is desirable to minimize the CTE of the encapsulant. For common encapsulants, there is an inverse relationship between CTE and modulus of elasticity. Thus, an encapsulant having lower CTE normally will have higher modulus of elasticity and higher shear modulus. Accordingly, the encapsulant 40 used in this embodiment desirably has a coefficient of thermal expansion less than about 200×106/° C. and more desirably less than about 100×106/° C. The encapsulant in this embodiment preferably has a modulus of elasticity between 0.1 GPa and 3 GPa, typically between 0.5 GPa and 3 GPa, as measured at room temperature. It is desirable to minimize variation in the properties of the encapsulant with temperature as, for example, in the range of temperatures from −65° C. to +125° C. As the thermal conductor 20 overlies the front or contact-bearing surface 35 of the die, that portion of the encapsulant disposed between the thermal conductor and the die will be in direct shear between the die and the thermal conductor due to differential thermal expansion and contraction of these elements. However, strain in this portion of the encapsulant is limited because the entire thermal conductor lies close to the center of the die. Moreover, the bond between the thermal conductor 20 and the thermal conductor mounting of the circuit panel 12, discussed further below, covers a substantial area and thus has substantial strength and fatigue resistance. For this reason as well, stress on this bond due to thermal effects tends to be less critical than stress on the bonds between the terminals and the contact pads. In a variant of this embodiment, the encapsulant may have non-uniform composition and properties as discussed below with reference to
The packaged semiconductor chip is provided with thin layers of solder 50 on the terminals 22, 22a and with a thin layer of solder 52 on thermal conductor 20. Such thin layers can be applied by application of solder paste and subsequent volatilization of the organic carrier from the paste or by wave-soldering or dip-soldering techniques. Desirably, the solder layers are less than about 75 microns thick, most preferably between 25 and 50 microns thick. The solder layers can be applied before severing the tape to form individual packaged chips.
In an assembly technique according to a further aspect of the invention, the packaged semiconductor chip is assembled to a circuit board or other circuit panel 12 as shown in
The thermal conductor 20 and the metallic bond between the thermal conductor and the thermal conductor mounting of the circuit board provide a thermally conductive heat transfer path from the die into the circuit board and also provide electrical shielding between the die and the circuit board. The entire structure is rugged and reliable. Inter alia, the bond between the thermal conductor and the thermal conductor mounting mechanically secures the packaged chip in place.
The packaged chip illustrated in diagrammatic sectional view in
Also, in the embodiment of
In the embodiment of
The packaged chip shown in
In the embodiment of
Other forms of leads can be employed. For example, as disclosed in U.S. Pat. No. 6,228,686, the disclosure of which is hereby incorporated by reference herein, a sheet-like element may include a main region and lead region which are partially segregated from the main region by slots extending around each lead region. The slot extending around each particular lead region is interrupted at a fixed end of the lead so that the fixed end remains attached to the main region of the sheet. The connection component diagrammatically depicted in
In the embodiments discussed above with reference to
Numerous further variations and combinations of the features discussed above can be utilized without departing from the present invention. For example, leads of the types shown in
A packaged semiconductor module according to a further embodiment of the invention (
The first electronic assemblage 602 overlies the top surface 638 of the chip carrier in the first region. The first or active chip 614 is connected by terminal lead 626 to the terminals 622 of the first set, and is also in thermal communication with the first thermal conductor 620. The relationship between the first chip 614 and the first terminals 622 and first thermal conductor 620 may be similar to those discussed above. For example, an encapsulant 641 having a relatively high thermal conductivity may be used to provide intimate thermal communication between the front or contact-bearing surface of first chip 614 (the surface facing downwardly in
Chips 606 and 608, constituting second assemblage 604 are mounted in essentially the same way and overlie the second region 633 of the chip carrier.
The module according to
The enclosure 671 provides mechanical protection and reinforcement to the packaged module. Moreover, the enclosure cooperates with thermal conductors 620, 621 and other metallic components of the chip carrier to provide electromagnetic shielding for the components in both assemblages 602 and 604. Additionally, the medial wall structure 675, in cooperation with central ground strip 662, provides effective electromagnetic shielding between the two assemblages. Thus, assemblage 602 is effectively isolated from assemblage 604. This arrangement can be used to provide such isolation for any type of electronic circuits. It is especially useful in the case where multiple electronic assemblages must be provided in a compact unit. Merely by way of example, modules according to this aspect of the invention can be used in elements of RF transmitting and receiving circuits of cellular telephones. In such a dual-band radio frequency power amplifier, one assemblage 602 provides a radio frequency power amplifier operating in a first frequency band, whereas another assemblage 604 provides a radio frequency power amplifier operating in another frequency band. Both assemblages can operate independently, without cross-talk or interference, even though the components of both assemblages tend to emit substantial amounts of electromagnetic interference. In a variant of the structure shown in
However, in the case where each unit includes passive components in addition to the active chip, fabrication of at least some of the passive components in each assemblage in an integrated chip, such as passive chips 615 and 608, makes the module considerably more compact than it would be if the passive components were provided as separate, discrete elements. Resistors and capacitors, in particular, can be fabricated readily in a chip. The materials and processing techniques to make the passive chips 608 and 615 may be different from those used to make the active chips 606 and 614. For example, the passive chips may be formed on materials such as glass rather than on silicon. In another example, the active chips may be formed in whole or in part from compound semiconductors such as III-V semiconductors or II-VI semiconductors, whereas the passive chips may be silicon-based chips. Thus, RF power amplifier chips formed from gallium arsenide and related semiconductors can be used in conjunction with silicon-based passive chips. In another example, the second or passive chips can be made with a larger minimum feature size or “line width” than the active chips, or vice-versa. Additionally, active chips originally made for use with discrete external passive components can be used in conjunction with the passive chips. Thus, compactness similar to that achievable by incorporating the passive components in the active chip itself can be achieved without the expense and difficulty of modifying the active chip itself.
Most preferably, at least some of the inductors used in the circuit are formed at least in part by the chip carrier or by the chip carrier in conjunction with leads and other structures extending to one or both of the chips. Although inductors can be fabricated in a passive or active chip, it is difficult to make inductors with high inductance and, particularly, with a high quality of factor or Q. The chip carrier typically is a “thick-film” structure, having metal layers more than about 2 μm thick, typically more than about 4 μm thick, and most preferably more than about 10 μm thick. Such thick layers commonly are formed by processes such as lamination of metal layers to a dielectric, plating or screen printing. Inductors formed at least in part in the chip carrier can employ large, thick, low-resistance conductors and can provide high inductance values with resistance far lower than that achievable in a thin film structure. Thus, it is desirable to provide at least some of the inductors incorporated in the circuit as structures defined in part or in whole by elements of the chip carrier, by leads extending between the chip carrier and a chip or both.
As depicted in
As schematically illustrated in
As shown in
As best seen in
In the embodiment depicted in
An inductor according to a further embodiment of the invention (
A component usable in a further embodiment of the invention is depicted in fragmentary view in
To form the indictor, the component is assembled with a chip, substrate or other element 880 (
A module in accordance with a further embodiment of the invention (
Chip carrier 918 has a hole 901 extending into the chip carrier from the inner surface 950. A metallic ring 911 is formed on the inner surface and surrounds hole 901. The metallic ring may be formed integrally with other metallic features on the inner surface, or may be separate therefrom. During manufacture, the front face 935 of chip 914 is juxtaposed with the inner surface of the chip carrier and is bonded to the chip carrier at ring 911. Thus, hole 901 provides a gas-filled cavity in alignment with the active surface region 902. The substrate does not contact the active surface region 902. A bonding material 903 desirably is provided between the inner surface of the chip carrier and the front face 935 of chip 914. For example, the bonding material may be a so-called “dry pad,” i.e., a pre-formed pad of a die attach material. The die attach material 903 is provided with a pre-formed hole prior to placing the die attach material between the front face of the chip and the chip carrier extending entirely around hole 901. The die attach material forms a seal between the front face of the chip and the inner surface of the chip carrier. During a subsequent stage of manufacture, encapsulant 917 is applied. The seal between the front face 935 of the chip and the inner surface of the chip carrier prevents entry of the encapsulant into hole 901. Alternatively or additionally, if chip 914 is provided with a ring-shaped metallic bond pad on its front face, the bond pad may be metallurgically bonded to ring 911 so as to form a similar seal extending entirely around hole 901 and active surface region 902.
Hole 901 desirably is closed or “blind,” so that the hole does not communicate with the bottom or outer surface 942 of the substrate. Hole 901 may be formed by any suitable technique used to for making blind vias in dielectric substrates. Desirably, hole 901 is partially filled with a metallic material. Thus, the hole 901 may have metallic via liner 907 extending along the wall of the hole. The via liner may join with a metallic element 909 on the outer or bottom surface of the substrate. This metallic element serves to close the hole. Moreover, metallic element 909 can be bonded by a solder mass 909, or other metallurgical bonding element, to a contact pad on the circuit panel. The via liner 907 thus serves as a heat-conducting element, so as to abstract heat from chip 914. In a variant of this structure, the chip carrier or substrate 918 is a “single metal” construction, with metallic features on only the outer or bottom surface 942, and hence ring 911 is omitted and hole 901 does not have a via liner. In a further variant, the substrate is a single-metal design with metallic features on only the inner or upper surface 950. The hole 901 in the dielectric of the substrate may be omitted, if ring 911 has sufficient thickness to maintain the active surface region 902 of chip 914 out of contact with the inner surface of the substrate. Alternatively, a hole may be formed partially or completely through the substrate within ring 911 to provide additional clearance. If the hole extends completely through the substrate, it may be closed by an additional element as, for example, a solder mask layer or other sheetlike structure applied on the bottom or outer surface of the substrate.
Structures according to this arrangement provide a gas-filled space in contact with the acoustic region of the surface acoustic wave chip, but also provide the other advantages achieved by mounting a chip in a package having a relatively thin chip carrier. Thus, the entire assembly can be substantially as compact as a unit which does not incorporate a surface acoustic wave device. Moreover, the structure is compatible from the manufacturing techniques used to make packaged chips and modules according to other embodiments of the invention, and the resulting packaged chip can be handled and mounted in the same manner as any other surface-mountable device. In the embodiments of
A packaged chip assembly according to yet another embodiment of the invention (
The second or passive chip projects outwardly in horizontal directions generally parallel to the plane of chip carrier 1018 beyond the edges 1021 of the active chip. The passive chip has outer contacts 1023 disposed beyond the edges of the active chip, and has conductors 1025 connected to these outer contacts. Conductors 1025 may connect directly with contacts 1019 and, hence, directly with contacts 1035 of the active chip. The passive chip also incorporates passive components, desirably resistors and capacitors, symbolized by a resistor 1027. As will be appreciated, a number of passive components may be incorporated within the passive chip. Also, some or all of the outer contacts 1023 of the passive chip may be connected to or through such passive components. If the package includes additional discrete components (not shown) or additional chips (not shown), the connections between outer contacts 1023 and inner contacts 1019 may include these elements.
The front, contact-bearing surface 1017 of the passive chip faces downwardly, toward the chip carrier or substrate 108. Thus, the outer contacts 1023 of the passive chip may be readily connected to the terminals 1022 of the chip carrier by leads 1026 similar to those discussed above. Moreover, because the rear surface 1044 of the active chip confronts the thermal conductor 1020, the rear surface of the active chip may be closely coupled to the thermal conductor so as to provide excellent heat transfer from the active chip to the thermal conductor and through the thermal conductor to the circuit panel. For example, the rear surface of the active chip may be coupled by a layer of solder or other metallic bonding material to the thermal conductor. The rear surface 1044 of the active die may be provided with recesses 1004 and rear surface contacts 1002 similar to the rear surface contacts 202 and recesses 204 discussed above with reference to
An assembly according to yet another embodiment of the invention (
In the embodiment of
A technique for making numerous packages incorporating spreaders or enclosures uses a substrate 1200 (
In the assembly method, the conductive sheet 1214 is assembled with the substrate sheet 1200 so that each region 1218 of the conductive sheet overlies one region 1202 of the substrate sheet, and so that the projections 1216 on the conductive sheet are aligned with enclosure openings 1212 of the substrate sheet. In the assembled condition, the projections 1216 extend from sheet 1214 to substrate 1200, leaving a gap or space between the sheet and the substrate. In the particular embodiment depicted, each projection 1216 extends through one enclosure opening 1212 and extends slightly below the bottom or outer surface of sheet 1200.
The chips and other elements to be incorporated in the packages are assembled to the sheets so that the elements to be incorporated in each package are disposed between a region of conductive sheet 1214 and the corresponding region of substrate sheet 1200. In the embodiment depicted in
Where the substrate sheet 1200 incorporates bond windows 1208 or other openings apart from the enclosure openings 1212, a cover layer 1224 is applied on the outer or bottom surface of the substrate sheet so as to close the bond windows after making the connections with leads 1206. In the next stage of the process, an encapsulant is injected between the substrate sheet and the conductive sheet. The encapsulant may be injected at one or more edges of the sheets or at one or more points along the extent of the sheets. Because projections 1216 are spaced apart from one another, they do not form continuous barriers and, accordingly, encapsulant can flow to all of the various regions 1202 of the substrate sheet. Thus, as schematically indicated by arrows 1228 in
After curing of the encapsulant, the sheets are severed as by cutting along cutting planes 1230 extending between adjacent regions 1202 of the substrate sheet and adjacent regions 1218 of the conductive sheet. The severing operation yields numerous units 1232 (
The side walls formed by spaced-apart portions 1234 have gaps 1236 corresponding to the spaces 1217 (
In the embodiments discussed with reference to
As illustrated in
The mating element 1380 used with this component is provided with two arrays of conductors 1382 and 1383, each such array also being arrayed along a similar path 1384. The conductors 1382 of the first set desirably are electrically insulated from adjacent conductors 1383 of the second set. Here again, the conductors 1382 and 1383 are generally elongated and extend generally transverse to path 1384.
In a manner similar to the assembly operation discussed with reference to
As in the embodiment discussed above with reference to
In the embodiment discussed above with reference to
In a further variant (
As these and other variations and combinations of the features set forth above can be utilized, the foregoing description of the preferred embodiment should be taken by way of illustration rather than by limitation of the invention.
Claims
1-10. (canceled)
11. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having a front face, a rear face, edges bounding said faces and contacts exposed at said front face;
- (b) a chip carrier having inner and outer surfaces, the inner surface of said chip carrier facing in an upward direction toward said first chip, said chip carrier having a plurality of terminals and a metallic thermal conductor exposed at said outer surface, said thermal conductor having area larger than the area of each of said terminals, said thermal conductor being at least partially aligned with said first chip, at least some of said terminals being electrically connected to at least some of said contacts of said first chip; and a connecting element having conductors thereon, said first chip being disposed between said connecting element and said chip carrier and connected to said terminals of said chip carrier through said conductors of said connecting element.
12. A packaged chip as claimed in claim 11 wherein said rear face of said first chip faces toward said chip carrier and said front face of said first chip faces toward said connecting element.
13. A packaged chip as claimed in claim 12 wherein said connecting element projects beyond said edges of said first chip.
14. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having a front face, a rear face, edges bounding said faces and contacts exposed at said front face;
- (b) a chip carrier having inner and outer surfaces, the inner surface of said chip carrier facing in an upward direction toward said first chip, said chip carrier having a plurality of terminals and a metallic thermal conductor exposed at said outer surface, said thermal conductor having area larger than the area of each of said terminals, said thermal conductor being at least partially aligned with said first chip, at least some of said terminals being electrically connected to at least some of said contacts of said first chip; and an electrically conductive element extending above said first chip.
15. A packaged chip as claimed in claim 14 wherein said conductive element includes a hollow can encompassing said first chip, said can having a top wall extending above said first chip and having side walls extending downwardly from said top wall.
16. A packaged chip as claimed in claim 15 wherein said side walls of said can are attached to said inner surface of said chip carrier.
17. A packaged chip as claimed in claim 15 wherein said side walls of said can extend outside of the periphery of said chip carrier and are exposed at the outer surface of said chip carrier.
18. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having a front face, a rear face, edges bounding said faces and contacts exposed at said front face;
- (b) a chip carrier having inner and outer surfaces, the inner surface of said chip carrier facing in an upward direction toward said first chip, said chip carrier having a plurality of terminals and a metallic thermal conductor exposed at said outer surface, said thermal conductor having area larger than the area of each of said terminals, said thermal conductor being at least partially aligned with said first chip, at least some of said terminals being electrically connected to at least some of said contacts of said first chip, wherein said thermal conductor and said terminals are disposed remote from said outer surface of said chip carrier and said chip carrier has apertures therein, said thermal conductor and said terminals being exposed to said outer surface through said apertures.
19. (canceled)
20. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having an upwardly-facing front face, a downwardly-facing rear face, edges bounding said faces and contacts exposed at said front face;
- (b) a connecting element overlying said front face of said first chip and projecting outwardly beyond said edges of said first chip;
- (c) a chip carrier extending beneath said rear face of said chip and having a bottom surface facing downwardly away from said first chip, said chip carrier having a plurality of terminals exposed at said bottom surface for connection to a circuit panel, at least some of said terminals being electrically connected to at least some of said contacts of said first chip through said connecting element, said chip carrier including a thermal conductor underlying at least a portion of said rear face of said chip in thermal communication with said rear face, said thermal conductor being exposed at said bottom surface of said chip carrier.
21. A packaged chip as claimed in claim 20 wherein said thermal conductor is metallic.
22. A packaged chip as claimed in claim 20 wherein said thermal conductor underlies at least a major portion of said rear face of said first chip.
23. A packaged chip as claimed in claim 22 wherein said thermal conductor is unitary.
24. A packaged chip as claimed in claim 20 further comprising an electrically conductive enclosure element overlying said connecting element.
25. A packaged chip as claimed in claim 24 wherein said enclosure element is a hollow can having a rear wall overlying said connecting element and having side walls extending downwardly to the vicinity of said chip carrier.
26. An assembly comprising a packaged chip as claimed in claim 20 and a circuit panel having contact pads and a thermal conductor mounting, said chip carrier being disposed on said circuit panel with said bottom surface of said chip carrier facing downwardly toward said circuit panel, said terminals of said chip carrier being connected to said contact pads of said circuit panel, said thermal conductor of said chip carrier being bonded to said thermal conductor mounting of said circuit panel.
27. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having an upwardly-facing front face, a downwardly-facing rear face, edges bounding said faces and contacts exposed at said front face, said first semiconductor chip including active components;
- (b) a connecting element including passive components, said connecting element being electrically connected to at least some of said contacts, said connecting element overlying said front face of said first chip and projecting outwardly beyond said edges of said first chip;
- (c) a chip carrier disposed below said rear face of said first chip, said chip carrier having a bottom surface facing downwardly away from said first chip and having a plurality of terminals exposed at said bottom surface, at least some of said terminals being electrically connected to at least some of said contacts of said first chip through said connecting element.
28. A packaged chip as claimed in claim 27 wherein said first chip includes active semiconductor components.
29. A packaged chip as claimed in claim 28 wherein said passive components in said connecting element include at least one passive component selected from the group consisting of resistors and capacitors.
30. A packaged chip as claimed in claim 29 further comprising at least one inductor formed at least in part on said chip carrier.
31. A packaged chip as claimed in claim 27 further comprising an electrically conductive enclosure element overlying said connecting element.
32. A packaged chip as claimed in claim 31 wherein said enclosure element is a hollow can having a rear wall overlying said connecting element and having side walls extending downwardly to the vicinity of said chip carrier.
33. A packaged chip as claimed in claim 27 wherein said chip carrier is a sheet-like element having thickness in the vertical direction less than about 150 microns.
34. A packaged chip as claimed in claim 33 wherein said chip carrier includes a thermal conductor underlying at least a major portion of said rear face of said first chip, said thermal conductor being in thermal communication with said first chip, said thermal conductor being exposed at said bottom surface of said chip carrier.
35. A packaged chip as claimed in claim 34 wherein said thermal conductor and said terminals are adapted for surface mounting to a circuit board.
36. A packaged chip as claimed in claim 27 wherein said chip carrier includes peripheral portions extending outwardly beyond the edges of said first semiconductor chip, all of said terminals being disposed in said peripheral portions.
37. A packaged chip as claimed in claim 27 wherein said connecting element is a second semiconductor chip.
38. A packaged chip as claimed in claim 37 wherein said first semiconductor chip and said second semiconductor chip include different semiconductors.
39. A packaged chip as claimed in claim 37 wherein said second semiconductor chip has minimum feature size larger than the minimum feature size of said first semiconductor chip.
40. A packaged semiconductor chip as claimed in claim 27 wherein said first semiconductor chip is a radio frequency power amplification chip.
41. A packaged semiconductor chip comprising:
- (a) a first semiconductor chip having a downwardly-facing front face, a upwardly-facing rear face, edges bounding said faces and contacts exposed at said front surface, said first semiconductor chip including active components;
- (b) a passive element including a plurality of passive components, said passive element having front and rear surfaces and contacts on said front surface, at least some of said contacts on said passive element being electrically connected to at least some of said contacts on said chip, said front surface of said passive element facing upwardly and confronting said front face of said first chip;
- (c) a chip carrier disposed below said rear surface of said passive element, said chip carrier having a bottom surface facing downwardly away from said passive element and having a plurality of terminals exposed at said bottom surface for connection to a circuit panel, at least some of said terminals being electrically connected to at least said chip, to said passive element, or both.
42. A packaged chip as claimed in claim 41 further comprising an electrically and thermally conductive enclosure element overlying said first chip.
43. A packaged chip as claimed in claim 42 wherein said enclosure element is a hollow can having a rear wall overlying said first chip and having side walls extending downwardly to the vicinity of said chip carrier.
44. A packaged chip as claimed in claim 40 wherein said chip carrier is a sheet-like element having thickness in the vertical direction less than about 150 microns.
45. A packaged chip as claimed in claim 44 wherein said chip carrier includes a thermal conductor underlying at least a major portion of said rear surface of said passive element, said thermal conductor being in thermal communication with said first chip through said passive element, said thermal conductor being exposed at said bottom surface of said chip carrier.
46. A packaged chip as claimed in claim 45 wherein said thermal conductor and said terminals are adapted for surface mounting to a circuit board.
47-54.(canceled)
55. A packaged module comprising:
- (a) a carrier having top and bottom surfaces and having terminals exposed at said bottom surface;
- (b) a first microelectronic unit mounted to said chip carrier and overlying a first region of said top surface;
- (c) a second microelectronic unit mounted to said carrier and overlying a second region of said chip carrier;
- (d) a metallic enclosure having a top wall structure extending above said microelectronic units and a side wall structure extending downwardly from said top wall structure to the vicinity of said carrier, said side wall structure including a medial wall extending to the vicinity of said carrier between said first and second regions and electromagnetically shielding said first and second microelectronic units from one another, said enclosure being in thermal communication with said microelectronic units.
56. A packaged module as claimed in claim 55 wherein said side wall structure includes one or more peripheral walls having bottom edges, said bottom edges of at least some of said peripheral walls being exposed at said bottom surface of said carrier.
57. A packaged module as claimed in claim 55 wherein said terminals are adapted for surface mounting.
58. A packaged module as claimed in claim 55 wherein said carrier extends generally in a plane, and wherein said enclosure has greater stiffness than said carrier in bending transverse to the plane of said carrier.
59. A packaged surface acoustic wave device comprising:
- (a) a surface acoustic wave chip having an active surface including an acoustic transmission region, said chip being operative to transmit acoustic waves along said active surface within said acoustic transmission region;
- (b) a substrate including a dielectric layer, said substrate having oppositely-directed inner and outer surfaces and electrically conductive elements on said dielectric layer, said substrate having a hole extending at least partially through said substrate from said inner surface, said chip being mounted on said inner surface of said substrate with said acoustic transmission region of said chip aligned with said hole so that said active surface of said chip in said acoustic transmission region does not contact said substrate, said chip being attached to said first surface of said substrate around the periphery of said hole.
60. A packaged device as claimed in claim 59 wherein said chip has contacts and said electrically conductive elements on said substrate include terminals exposed at said outer surface, at least some of said terminals being connected to at least some of said contacts.
61. A packaged device as claimed in claim 60 wherein said contacts are disposed on said active surface of said chip outside of said acoustic transmission region.
62. A packaged device as claimed in claim 61 wherein said substrate has one or more apertures extending through said dielectric layer in alignment with said contacts, said device further comprising leads extending to said at least some of said contacts through said one or more apertures, said at least some terminals being connected to said at least some contacts by said leads.
63. A packaged device as claimed in claim 62 wherein said conductive elements on said substrate include a metallic ring on said inner surface surrounding said hole and wherein said active surface of said chip is bonded to said metallic ring.
64. A packaged device as claimed in claim 61 wherein said hole extends through said dielectric layer of said substrate, said conductive elements of said substrate include a metallic via element surrounding said hole at least at said second surface, and said device further comprises solder masses on said terminals and on said via element.
65-75. (canceled)
76. A method of making a plurality of microelectronic assemblies comprising the steps of:
- (a) assembling a substrate sheet including a plurality of regions with a top sheet having spaced-apart projections thereon subdividing the conductive sheet into a plurality of regions so that each region of the substrate sheet is aligned with a corresponding region of the conductive sheet, so that there is a gap between the conductive sheet and the substrate sheet and so that projections on the conductive sheet extend from the conductive sheet into proximity with the substrate sheet;
- (b) providing microelectronic elements between the substrate sheet and the conductive sheet; and
- (c) injecting an encapsulant into the gap so that the encapsulant flows between the conductive sheet and the substrate sheet and so that the encapsulant flows through spaces between the projections and onto a plurality of the regions of the substrate sheet.
77. A method as claimed in claim 76 further comprising subdividing the sheets after said injecting step so as to form a plurality of units, each including at least one region of the substrate sheet, at least one region of the conductive sheet, one or more microelectronic elements and side walls extending between such regions formed from the projections.
78. A method as claimed in claim 76 wherein the top sheet and the projections are electrically conductive.
79. A method as claimed in claim 76 wherein the substrate sheet has enclosure openings bounding the regions of the substrate sheet, said assembling step being performed so as to engage the projections on the top sheet in the enclosure openings.
80. A method as claimed in claim 79 wherein the projections and the enclosure openings are arranged in rows.
Type: Application
Filed: Aug 28, 2002
Publication Date: Mar 3, 2005
Patent Grant number: 7566955
Applicant: Tessera, Inc (San Jose, CA)
Inventor: Michael Warner (San Jose, CA)
Application Number: 10/488,210